Ethylene-α-olefin-polyene copolymers such as ethylene-propylene-dicyclopentadiene copolymers are widely used as materials for automobiles, industrial apparatuses, OA apparatuses, construction materials, etc. As a process for producing the ethylene-α-olefin-polyene copolymers, there is known a process which comprises preparing two kinds of ethylene-α-olefin-polyene copolymers and melt mixing them for obtaining polymers having desired physical properties depending on the use.
As other process, there is known a process for producing an ethylene-α-olefin copolymer by continuous multistage polymerization using a multistage polymerization reaction apparatus comprising two or more tanks of polymerization reactors connected in series. For example, Patent Documents 1 and 2 disclose a continuous multistage polymerization of ethylene, propylene and 5-ethylidene-2-norbornene by carrying out a first polymerization in a first polymerization reactor and then feeding the whole of the resulting reaction mixture, an additional solvent, additional monomers and the like to a second polymerization reactor of the same volume as the first polymerization reactor, and carrying out a second polymerization in the second polymerization reactor. Patent Document 2 discloses that the production process by a continuous multistage polymerization is economically advantageous.
(Patent Document 1) JP-A-57-131212
(Patent Document 2) JP-A-2002-505357